I’d be more of build-up. It doesn’t confirm WHY they abandoned her. Also in TFA and TLJ pre-throne room they already give out evidence and hints of Rey’s insecurities. (That’s also my Reddit post.)
In the previous Force bond scene (which takes place right before the mirror scene) Rey denies that her parents abandoned her, so it would kinda be a whiplash 180 turnaround moment imo.